This invention relates to a water-cooled internal combustion engine, and more particularly to an improved temperature control system for such an engine.
The use of water cooled internal combustion engines are well known. Frequently these engines comprise a plurality of cooling jackets surrounding various portions of the engine and through which cooling water is circulated in a predetermined pattern. One reason for using separate cooling jackets is that some components of the engine require greater cooling than others. For example, the cylinder head generally provides a greater heat load than the cylinder block. Therefore, it has been the practice to provide separate cooling jackets for the cylinder head and cylinder block that are interconnected in a flow path. Normally the cold water is first delivered to the cylinder head and then passes to the cylinder block.
Although these arrangements are highly satisfactory, frequently the cooling requirements of different components of the engine can vary during the running condition of the engine. For example, in the induction system it is desirable to provide a low temperature when running at high speeds and high loads. Such cooling improves the volumetric efficiency. On the other hand, when running at low speeds and low loads and under low ambient temperatures, excessive cooling of the induction system can cause condensation and poor fuel economy. These problems are particularly acute in two cycle crankcase compression internal combustion engines.
In two-cycle crankcase compression internal combustion engines, the fuel/air charge is drawn into the crankcase and is compressed during the stroke of the piston for transfer to the combustion chamber through one or more transfer or scavenge passages that interconnect the crankcase with the portion of the cylinder bore above the piston at certain phases of its stroke. Such engines have the advantage of extreme simplicity and, for that reason, are popular in many applications. However, the long path through which the fuel/air mixture must travel before it enters the combustion chamber presents certain problems. For example, when operating at low temperatures and under certain other operating conditions, there is a tendency for a portion of the fuel to condense from the fuel/air mixture in the crankcase. If this condensed fuel is transferred into the combustion chamber through the transfer or scavenge passages, the fuel/air mixture is irregular in strength and poor running can occur. These problems are particularly acute under idle, low speed, acceleration and deceleration conditions.
Thus, it is clear that there are advantages to heating the induction system and crankcase when operating at low ambient temperatures, low loads and low speeds. However, the heating of the induction system and the crankcase chamber in a two cycle engine will adversely affect the fuel economy and power output of the engine when operating at high speeds, high loads and normal temperatures.
It is therefore, an object of this invention to provide a liquid cooling system for an engine wherein certain portions are cooled more rapidly than others under some running conditions and those same certain portions are heated more rapidly under other running conditions.
It is an object of this invention to provide a temperature control system for an internal combustion engine which prevents the formation and accumulation of condensates in the crankcase chamber or in the transfer or scavenge passages.
It is a further object of this invention to improve the output of an internal combustion engine by increasing the air charge amount into the combustion chamber within its high load operation range and/or to stabilize combustion by promoting carburetion of fuel within its low load operation range.